Purification of natural deposits



Feb. 9, 1937. R. w. FLINN 2,070,161

PURIFICATIOI OF NATURAL DEPOSITS Filed Jan. 21, 1935 SANDS a c1. A vs GRADE/P EXHAUST OF VOLA TILES HE A 7' 8 AG/ TA T/ON CHL OR/NE 6A 5 CONDENSER STORAGE CONDENSA r5 INVENTOR.

ROLAND n. FL/NN. BY

Patented Feb. 9, 1937 UNITED STATES PATENT 4 OFFICE 1 Claim.

My invention relates to the purification of nat ural deposits and more particularly, to the purification of sands. My invention is particularly useful in the purification of silica sand for use in 5 making of glass.

Among the objects of my invention are: To provide for the purification of silicious sands; to provide for the purification of natural deposits whereby the iron content may be greatly reduced; to provide a method of treating natural deposits to'recover therefrom the greater portion of the iron content; to provide a method whereby the greater portion of the aluminum content of natural deposits may be removed;

to provide a method whereby stained silicious sands may be used in the making of clear glass; to provide a method for the removal of iron stains from natural deposits such as silica sands and ceramic clays; to provide a method of treatin natural sand deposits whereby the material of the deposit may be obtained in purified condition and the removed impurities collected for separate use, if desired.

Other objects of my invention will be apparent orwill be specifically pointed out in the description forming a part of this specification, but I'do not limit myself to the embodiment of the invention herein described, as various forms may be adopted within the scope of the claims.

The figure represents a flow sheet of a preferred method for removing iron stains from silicious sand, together with a substantial amount of any aluminum content present in the deposit.

No natural sands are entirely free from iron compounds and even the most stringent attempts heretofore attempted at purification do not succeed in completely removing all the iron present. The chief compounds of iron occurring in sands are the'oxides, carbonates and sulphides, and va- 40 rious other complex minerals containing irons. These. compounds are derived from decomposed ferruginous rocks either by direct admixture or by the compounds being dissolved by organic acids, the solution formed thereby running over,

penetrating the sands, staining. them, and in many cases, being later decomposed.

Iron compounds may occur in sand in three forms: (a) as a thin film coating the grains of other minerals; (b) in minute particles disseminated fairly uniformly through the sand; and (c) as larger particles gathered irregularly amongst the grains of other materials.

The chief effect of these iron compounds in sands or similar deposits is to reduce their refractoriness and to cause them to be brownish in color. The intensity of the color produced by the presence of iron is not, however, a reliable indication of the amount present, as much depends upon the condition and nature of the iron compounds and whether or not the iron is dis- 5 .seminated throughout the sand as specific iron particles or as a film over the grains of the sand itself. It is with this latter condition where the iron is present in the form of a stain that the instant application is concerned, as there are 10 other methods known in the art for dealing with specific iron particles.

It is well known in the art that where a sand contains a very adherent film of iron oxide or limonite, washing will not improve it to any 15 great extent and in the use of sand for glass manufacture, if the proportion of iron oxide is high, the sand heretofore has been completely rejected.

It is standard in the art that sands for use in 20 the manufacture of the best glasses should not contain more than a total of 1% of these impurities, including iron, and in most cases, sand should be used with less than half of this percentage of impurity. In fact, the best quality optical glass, 25 in order to be perfectly colorless, can only be produced from sands containing not more than .03% of iron oxide, this proportion being'reduced in the final glass to .02% due to the fact that only about two-thirds of the batch composition is 30 sand.

Iron. compounds are not alone objectionable in sand to be used for making glass, but others, such as aluminum, vegetable and organic matter, are also highly objectionable. 35

Alumina occurs in glass sands principally as orthoclase, feldspar, muscovite clay, and alumino-silicates. The muscovite and clay may be removed fairly readily by washing; but the others cannot be removed in this manner. 40

In small proportions aluminum is useful in sands used for making glass of a certain quality in that it tends to invest hardness, brilliancy and strength and reduce the coefiicient of expansion. The chief disadvantages are that it decreases the fusibility, increases viscosity and creates a glass which does not mix readily with others. It is, however, undesirable in optical glasses where not more than .5% of alumina 50 should be present. .On the other hand, dark glass bottles often contain as high as 4% of alumina. The instant invention is also concerned with the lowering of a higher aluminum content in a sand to a point where glass made therefrom will be perfectly satisfactory even for of the manners well known in the art to prevent escape of the chlorine and compounds formed therefrom. v

At a suitable location intermedlately between the two ends of the tube, the tube is perforated mg, a certain amount of organic matter is not and an exhaust ring or similar means positioned only not harmful to my method, but in certain around the tube to collect the volatile comcases is actually beneficial, as will be pointed pounds given off, and I prefer .to conduct the out later. gases removed from the oven through a con- Heretoforethe purification of sands or similar denser of any convenient form and to apply deposits such as ceramic clays which are stained ne a ive p es ure t h xh y m an f with iron, have been purified by the application ny ui l p p or like d vice. In order that oi hydrochloric acid in the form of a wet treatt e nd s r a d p p ay n t become g d ment. It is also known in the art that sands ith s d p i s d d st, I p r t p imay be mixed with common salt and sulphur tion a filter immediately adjacent the drum in and heated to redness, but neither of the two the exhaust linemethods heretofore used is satisfactory for As the send progresses speedy and continuous purification of sdnd det high end to h heated lower t is a posits nor have the processes heretofore used uelly heated a d as t app s 0, th r n been adapted to the removal of excessive content of the sand combines with the chlorine amounts of aluminum, My invention, however, .to form iron chloride which, being volatile passes provides broadly, for the continuous removal of Off through h exhaust tube n is Condensed as iron stain, and for either the simultaneous or an q u uti of iron chloride t As two-step removal of both iron and alumina bethe send progresses s f d pp a low the minimum requirements of the making 600, the aluminum Present starts to Combine of e pfical glasses. with the chlorine and forms aluminum chloride, The broad steps in my preferred t d which is also volatile and is recovered in the conprise the passage of washed and graded sands dehsels as aluminum ehlmidethrough a heated chamber w t the continuous in this case will contain both the iron and alumiapplication of chlorine g meanwhile, mnum chloride,'and it may be removed and treated taining agitation -of the particles until the iro further if desired to recover iron or aluminum or combines with the chlorine to form iron chloboth as hy-ploduetsride, which is volatile and which is exhausted If desired, however, the 11011 and ell-111111111111 from the chamber. I have found that this commay e collected pa e y by e u o tw e bination takes place when the sand is between heust llnes, One On each s1d e 0f divisieh in the 200 and 300 degrees Centigrade and above, and drum by a trap thlc'ugh which the can passt t if the temperature be raised t over 600 This division is made between the POItlOIiS 0f the the aluminum also combines with the chlorine, drum below 00 and that portionof the drum passing oi as a1um1num,ch1flde Both of these above 300, so that relatively pure separate concmorides may be condensed a use of tdensates of iron chloride and aluminum chloride able condensers and removed as aqueous solumay be obteihed- This Procedure, hWTeVer is tions, the water coming from the moisture of the Purely optimal and depends P011 the means and sand as originally introduced into the n method by which the metals are to be recovered It has heretofore been known that aluminum the condensatesoxide can be treated with chlorine, using char- The amount of iron remaining in the sand is coal as a catalyst There is however, usually less than .03% after treatment with the chlorine suilicient organic material in the sand as ingas and the amount'of aluminum remaining will troduced into the heated .chamber to provide for Of course depend upon the Original amount 1n h the catalytic action, or if necessary, small sand, the, length of time the sand is heated to amounts of carbon may be introduced into the the higher temperatures. an t the and temoven as will be later described; Pereture to Y Specifically, I prefer to describe my process as heeted end the in u e. applied to the purification of a silicious sand The h s Obtained y my process s almost containing more than .03.% iron in the form of pure Whlte, 1s P e tly satisfactory for ass a stain and from 337% t alumina r mixesand my process is such that the residual sand as mined isnot suitable for glass manuimpurities can be accurately eentlelled y adfacture. After excavation, the sand is washed lusting the length of the tube d t e'degree of and graded in accordance with the requirements heat, as pointed out above. The entire process of theglass industry as well known in art, being a continuous one, the sand can be treated and i then passed into any suitable form of at a very low expense, thus making available for oven t be treated. I pref r however, to use the use of glass factories huge deposits of sand a rotary calcining oven similartothat used m which have heretofore been rejected because of he impurities therein. the cement industry. where a long tube is posit tioned on rollers and rotated at a slight angle It should also be pomted out that Should any so that the sand mtmduded at one end will organic matter be present in the sand, it will be 3 carbonized by the heating process to provide the lowele l i s g rz id e v igz 1: hz ofe heat i g at 25 5 i011. the g g the c orine e auminum. s cen ormf so h g z pogreiswely ganic matter is not present in the sand as inzz g g 3 s z e troduced, the heating flames which are posirme jets whereby gt-sews :h g :i :& tioned at the lower end of the oven can be ad-- Y justed to supply to the interior of the tube a to the rotatin t be- The entrance of the send sufficient amount of carbon to thoroughly and at the high-end and the outlet'of the sand at completely aid the combining of the two the low and may be blocked or trapped in any materials. N

optical purposes.

Organic matter should not be present in sands used for I glass making and while a great deal of this organic matter may be removed by washwhich the sand is subjected at the through the oven from The condensate It also is very simple to make the process completely regenerative ifthe refining of the iron and aluminum chlorides is done in such a manner that the chlorine can be removed from the condensate and returned to the jets. My preferred process contemplates such regeneration. Substantially the same apparatus will be used when surrounding clays are beingtreated, or in fact any natural deposits wherethe impurities,

particularly iron, in the form of stains, exist on the outside'of the particles. t

It'will be obvious to those skilled in the art that my process can be accomplished by the use of the' assembly of many types of suitable machines now in usein the art for other purposes,

I claim:' a The method I finely divided form 'in an oven which comprises passage through said oven to obtain "intimate mixture of gas and material particles, applying a heat gradient to said streamsthrough said oven whereby different, combinations of the gas' and impurities in said oven will occur in difierent 10- cations within said oven, and separately remov-,-.

ing said different combinations. V

' ROLANP W. FLINN.

the apparatus as outlined above being exemplary I only. I

of purifying naturaldeposits 'in passing. said material continuously through said oven, passing a continuous stream of chlorine gas through said oven, agitating said material during 

